The present invention relates to an improvement in scrolling color illumination, which is presently implemented in a single panel liquid crystal (LC) projection system that is suitable for television. The improvement is a system that is suitable for demanding computer monitor applications.
Scrolling color illumination was patented and implemented in a single panel LC projection system by Philips Electronics North America Corporation, showing a picture quality deemed suitable for television. Computer applications are much more demanding than television because some computer-generated patterns can provoke color break-up, an artifact common to all color sequential displays, much more easily than natural television images. This color break-up makes it more difficult for a color sequential system to penetrate the personal computer monitor market.
Color flashes can be observed in high contrast patterns through rapid eye movements, for instance when blinking. Human sensitivity to this artifact can be explained as a discrepancy between the exposure of the retina""s peripheral vision to colored light and the black and white image the central vision system was adapted to.
As prior art, there may be mentioned: U.S. Pat. No. 5,845,981; EP 601,666; EP 492,721; U.S. Pat, No. 5,428,467; WO 95/26110; Kokai 08-211,358, 08-022,006. None of these references shows a continuously scrolling architecture, which is characteristic of the scrolling color illumination systems of the invention.
It is an object of the present invention to provide improved scrolling color illumination suitable for use in computer monitors.
It is an object of the present invention to provide scrolling color illumination that is suitable for use in a rear projection desktop monitor.
It is another object of the present invention to provide multiple color stripes to suppress color artifacts in computer displays.
These objects, as well as further objects which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, by a scrolling multi-stripe color illumination system comprising means for generating more than three color stripes and a means for scrolling the multiple color stripes.
Single panel scrolling color projection systems using three (red, blue and greenxe2x80x94RGB) scrolling color bands have been demonstrated to be adequate for television images. However, computer graphics are more prone to color artifacts. The invention increases the number of scrolling color bands in order to suppress these artifacts. One implementation of the scrolling multi-stripe color illumination system comprises breaking up the three color stripes into multiple stripes using a lenticular lens array, collimating the multiple stripes with a second lens array, and scrolling the collimated stripes using a rotating prism of the prior systems.
Another implementation of scrolling multi-stripe color illumination system of the invention comprises a polarizing beamsplitter, which reflects light from a source through a lens subsystem and a quarter waveplate onto a rotating drum, from which multiple colored stripes are retro-reflected back through the lens subsystem and the quarter waveplate, which enables the retro-reflected light to pass through the polarizing beamsplitter, and the retro-reflected multiple colored stripes produced are directed onto a light valve, producing a scrolling pattern of colored light.
By exposing the eye to multiple color stripe images, rather than a single one, during rapid eye movements, the impression of a different color in the peripheral vision region is removed. The scrolling color system lends itself particularly well to such a solution. Unlike the xe2x80x9cwrite, wait and exposexe2x80x9d sequence used in other color sequential systems, the system of the invention enables continuous addressing of an arbitrary number of color stripes without adding overhead.